开放条件下粒径对块石和碎石护坡降温效果影响的试验研究

Experimental investigation on influence of grain-diameter on cooling effect of crushed rock revetment with permeable boundary

对开放条件下,粒径对块、碎石护坡降温效果的影响进行了一系列试验研究,试验中选择的粒径范围为:6～8、14～16、21～23、28～30 cm。结果表明:迎风与背风两种条件下,4种粒径块、碎石护坡均具有较好的降温效果,均可在第2个试验周期将其下部土坡表面平均温度迅速降至0℃以下,有效地对其下部土体进行降温。在迎风条件下,粒径在6～30 cm内,块、碎石护坡降温效果随粒径的增大而加强;背风条件下,块、碎石护坡降温效果在粒径为21～23 cm时最好。在外界气温等同的条件下,块、碎石护坡底部温度周期变化幅值主要受到迎风与背风条件的影响,块、碎石粒径的作用并不十分明显,即在迎风条件下,块、碎石护坡底部温度变化幅值远大于背风条件,并且每个试验周期中迎风护坡底部的正温高于背风护坡,且维持时间较长,这将不利于冻土路基的稳定。

A series of experiments were constructed for the cooling effect of crushed rock revetments with different grain diameters under permeable boundary condition. The grain-diameters of crushed rock included four kinds： 6-8, 14-16, 21- 23, 28-30 cm. The experimental results indicated that, under the windward and leeward conditions, the cooling effect of crushed rock revetments with all these four grain-diameters was good and could effectively reduce the temperatures of the underlying soil layers; furthermore, the mean periodic temperatures of soil slope surfaces under crushed rock revetments could be lowered down below 0 ℃ after two experimental cycles. Under windward condition, with the increase of grain diameter, the cooling effect of crushed rock revetment became better when its grain diameter ranged between 6 and 30 cm; under leeward condition, the cooling effect of crushed rock revetment with a grain diameter range of 21-23 cm was best. Besides, It was found that, under the experimental condition, the periodic temperature at the bottom of crushed rock revetment was mainly dominated by windward/leeward condition, and not by grain-diameter of crushed rock. Namely, the periodic temperature at the bottom of windward crushed rock revetment was far larger than that at leeward one, and the positive temperature range at the bottom of crushed rock revetment under windward condition in every cycle was far higher than that under leeward condition. Furthermore, the duration of the positive temperature was longer under windward condition. Therefore, it would be disadvantageous to the stability of permafrost embankment.